The present invention relates to a single-use, disposable optical cell and cartridge with associated optical interface for use in conjunction with an optical instrument for analysis of fluid samples and the materials therein.
Measurement of characteristics of fluids by optical means is well-known in the art. The ability to characterize a fluid non-destructively is useful in many industrial and laboratory applications such as bioprocessing, chemical processing, food and beverage manufacturing, petroleum processing, and pharmaceutical manufacturing. Electromagnetic radiation impinging on a fluid medium may interact with the medium by absorption, scattering, or fluorescence. Measurement of transmitted, reflected, scattered, or fluoresced radiation by an appropriate set of detection optics may be used to determine characteristics or properties of the medium such as concentrations of chemical analytes or turbidity.
Several common approaches exist for providing optical access of analyzers and spectrometers to fluid samples. Manual introduction of fluid samples to optical instruments by cuvettes or similar sample containers is a standard method for performing discrete sample measurements. Such containers are often disposable items and the fluid sample introduced to the container is most commonly discarded after measurement, especially if the fluid is drawn from a sterile process. While cuvettes or similar disposable cells may be configured in a motorized tray or carousel assembly to permit automated measurements of several samples, such measurements are of limited value for continuous, long-term monitoring or when high time resolution is required.
Many varieties of fluid cells also exist in the prior art. Unlike cuvette-type approaches, cells permit continuous delivery of fluid to a measurement apparatus. Process cells comprising a machined housing with connectors for optical fibers and inlet/outlet tubing are common prior art examples. These assemblies often comprise parallel window geometries whereby fluid traversing the windows is optically interrogated by electromagnetic energy delivered and collected by optical fibers. Such assemblies are often machined from metal or plastic, are intended to be used multiple times, and are designed to withstand harsh process conditions such as high pressure, high temperature, and extended contact with corrosive solutions. Cells for such demanding environments are typically costly and inconvenient to incorporate in processes that require sterilization of all wetted surfaces. Furthermore, many examples comprise optical materials that are intended for ultraviolet (UV), visible (VIS), and telecommunications wavelengths which span approximately 200 to 1600 nm. Such materials typically have poor optical transmission in infrared wavelengths beyond 1600 nm, and are thus unsuitable for optical instrumentation utilizing that region of the electromagnetic spectrum.
Numerous branches of industry and science increasingly prefer so-called “single-use” or “disposable” components in fluid processing applications. The ease of use of disposable components such as processing vessels and sensors is particularly attractive in, for example, biological applications where sterility is of the upmost importance. Single-use, disposable components may be offered to the end user pre-sterilized, and no costly cleaning procedures are required after the fluid processing has terminated—the user may simply discard the disposable component. It is therefore desirable to design components that come into contact with process fluids as single-use, disposable items if at all possible.
Disposable flow cells have been demonstrated in the art. Some examples are simply less costly plastic analogs to the previously described process cells, but suffer from the same limitations. Other examples utilize a disposable cell assembly situated within optical elements and a housing assembly that may be disassembled such that the flow path is unbroken. Despite the merits of such examples, prior art implementations have often been specific to spectroscopic measurements in the UV and visible electromagnetic spectrum, require inconvenient assembly and disassembly procedures, and are not well-suited for infrared spectroscopic applications.
Another common limitation of prior art cell designs is that assembly and disassembly steps are required in the fluid flow and/or optical paths to connect cells to a process. In the case of common reusable process cells, a typical configuration includes fluid connectors coupled to the cell for attachment of tubing lines to carry the fluid to the measurement zone of the cell. In this configuration, insertion or removal of the cell from the flow path requires coupling or decoupling of the tubing from the connectors. Such manual intervention is often undesirable, especially in closed-loop and sterile processes. Disposable cells, on the other hand, are in some cases able to leave the flow path unbroken during insertion or removal of the cell from the flow path. However, prior art versions require manual assembly and disassembly of mechanical components to access the disposable cell, and this level of user intervention is often undesirable and inconvenient.
To overcome the limitations of prior art methods of optical interfacing with fluid samples, an optical cell apparatus is desired in which the optical path length is stable, all components in the optical path are constructed from materials highly transparent within the spectral range of the analysis, and all materials that contact the fluid are disposable and may be sterilized by common means. The disposable cartridge and tubing contained therein would desirably be of sufficiently low cost to render it a consumable which may be regularly replaced, and replacement should desirably be feasible by unskilled personnel and require minimal, if any, assembly or disassembly of mechanical components. Furthermore, said disposable cartridge may desirably be removable from the optical instrument during a continuous, closed-loop process without compromising any fluid seal or the sterile environment within the cell as well as be capable of being reinserted to resume measurements. The apparatus also would desirably be amenable to both free-space and optical fiber based coupling approaches.